1. Field of the Invention
The invention relates to surgical staples and more particularly to a surgical staple having advantages in orthopedic surgery for repairing bone fractures and like defects.
2. Brief Description of the Prior Art
The simplicity of using a surgical staple has always been attractive to the orthopedic surgeon, the potential speed of their insertion being an obvious advantage over the use of bone screws. In fact, staples have been used by the orthopedic surgeon to repair bone fractures since the early 1940's. With the development of physiologically acceptable materials such as stainless steels, it became possible to leave the staple in place after the bone fracture healed.
As materials for fabricating staples developed, the Chrome-Cobalt series of heavier, harder staples became available, having some advantages. However, these staples have a greater use for the reattachment of ligaments to bone than for use in bone to bone fixation of fractures.
The Coventry staple was developed for fixing osteotomies and maintaining bone positions while an external cast was applied. This was the first serious recognition and use of a staple as a means of bone to bone fixation.
In more recent years the Shapiro staple with the aid of a power inserter has enabled the orthopedic surgeon to rapidly insert a plurality of staples into bone, to fix the fractured surfaces into position for healing.
However, the use of staples for bone to bone fixation along a fracture line has not won complete acceptance by the surgeon. In the early uses, insertion of the staple was carried out with a simple holding instrument and a hammer to drive the staple legs into the bone. This often caused the separate bone moieties to move from their desired positions before completion of the insertion. The use of the power driven hammer and the Shapiro staple did not completely obviate this problem even though the increased speed of insertion might be expected to alleviate it.
The correct positioning of the fractured surfaces of a bone is important to promote healing. A fracture is generally accompanied by a hemorrhaging of the periosteum at the fracture site. Fibroblasts and capillaries grow into the resulting blood clot to form granulation tissue and plasma and white blood cells exude into the tissue to form a viscous callus which serves to adhere the fractured bone surfaces together during the healing process. Bone cells from the periosteum and calcium salts are deposited in the callus to harden and form new bone. Ideally, to speed ossification the bone interfaces at the fracture site are held together under compressive forces. Otherwise, if the interfaces are held apart either under neutral or tension forces, fibrous ingrowth may occur rather than new bone development. This condition, known as "fibrous union", represents a failure of treatment. For this reason, the orthopedic surgeon has been wary of using staples to achieve bone to bone fixation in many circumstances.
In the absence of a reliable stapling procedure, the art presently resorts to fixation means and devices which permit the surgeon to place the fractured bone interfaces together under compression. Compression is obtained either after inserting the device and requiring the patient to put pressure on the bones (for example with application of the Richards hip screw or the Kutchner intramedullar rod) or by mechanically adding compression via a screw mechanism (such as in compression plates, dynamic compression plates or external fixation devices; see also the compression nail device described in U.S. Pat. No. 4,574,795). It will be appreciated that these procedures require major instrumentation and operative skills with significant surgical exposure and risk.
Also representative of prior art bone staples are those described in U.S. Pat. No. 4,570,623 and in the European Patent Application 0 301 896, both of which describe staples with serrated or toothed legs.
The staple and method of the present invention represents an improvement in the orthopedic arts, permitting bone stapling to achieve bone to bone fixation under compression of the fracture interfaces. The procedure is simple, quick and efficient, minimizing surgical exposure and risks. The staple and method of the invention can be used to fix even small, multiple fragmented bone fractures employing a series of staple insertions.